Turbine engines, and particularly gas or combustion turbine engines, are rotary engines that extract energy from a flow of combusted gases passing through the engine in a series of compressor stages, which include pairs of rotating blades and stationary vanes, through a combustor, and then onto a multitude of turbine blades.
Gas turbine engines have been used for land and nautical locomotion and power generation, but are most commonly used for aeronautical applications such as for airplanes, including helicopters. In airplanes, gas turbine engines are used for propulsion of the aircraft.
Gas turbine engines for aircraft often require lubrication of moving components. In order to keep these components lubricated, oil or an oil/air mixture is fed through the engine to these components. This causes the oil to become hot. Hot oil can be used to warm fuel, while simultaneously cooling the oil. Typically, an oil cooler heat exchanger and an oil tank are separate components. Sometimes the oil cooler heat exchanger is mounted to a fuel manifold that is also common to the oil tank, and oil is piped from various locations such as the main gearbox lubrication system and engine lubrication system. However, these are typically kept as entirely separate systems for reasons associated with safety of flight.